<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>三个等于号</title>
		<script>
			var a="4";
			var b=4;
			alert(a==b);
			alert(a===b);
		</script>
	</head>
	<body>
		<input type="number" name="sal" />
	</body>
</html>